This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Rotating frame relaxation MRI contrast, T1rho and T2rho, are thought to provide sensitive indicators of tissue changes in hyperacute stroke. In this work, we are investigating the changes in T1rho and T2rho MRI of infarcting brain, and have recently shown that the changes in hyperacute stroke reflect an increase in the free water pool size, decreased tumbling of the water molecules associated with macromolecules, and increased water exchange between free and macromolecular sites. These findings are consistent with vasogenic edema, destructive processes and tissue acidification. This research is providing new insights into the physico-chemical processes occurring in brain ischemia